Stigmergy is a notion that an agent's behavior is sometimes best understood as coordinated by the agent's environment. In particular, social insects build nests, which have a recognizable standard pattern (different patterns for different species). Does the wasp or termite have an idea of what the standard pattern is? Probably not. Instead, the computation inside the insect is a stateless stimulus/response rule set. The partially-constructed nest catalyzes the next construction step.

An unintelligent "insect" clambering energetically around a convoluted "nest", with the insect's local perceptions driving its local modifications is recognizably something like a Turing machine. The system as a whole can be more intelligent than either the (stateless) insect or the (passive) nest. The important computation is the interactions between the agent and the environment.